Conventional ski bindings prevent ski injuries by releasing the skier's leg from relatively stiff communication with the ski when forces deemed to be injurious are applied to the ski, as in a ski fall. Early ski bindings held the ski boot, and thus the leg and ankle of the skier, in firm communication. It was soon realized that the twisting loads that the ski can apply to a falling and tumbling or rolling skier can be substantial. So called “safety bindings,” which maintain communication, i.e., transmit loads, between boot and ski only up to a predetermined threshold force, and are intended to release the ski before a lower-extremity equipment-related (LEER) injury occurs, have been the norm for more than forty years.
Modern ski bindings have a heel and toe pieces for retaining corresponding portions of a ski boot (boot), typically in spring loaded cam devices with toe and heel cups adapted to engage a protrusion on the boot heel and toe. The spring loaded cam systems allow the toe and heel cups to rotate and release the boot to prevent the transmission of potentially injurious loads to the skier. Typically, rotation of the ski boot out of alignment with the toe of the ski occurs from pivoting or rotating movement of the cups on the binding toe or heel pieces. The toe and heel pieces are set to retain the boot in engagement with the ski, typically by preloading the release spring in a spring-cam biased retention system. When certain bending, twisting or rotation loads exceeding certain predetermined loads occur, the binding heel piece allows the heel cup to rotate up, and on some bindings laterally as well, or the binding toe piece allows the toe cup to pivot right or left, and on some designs up as well, to allow the boot to release from the ski and binding, typically from a downed skier rolling or tumbling across the snow surface. The threshold release loads for the toe and heel pieces, however, need to be identified, adjusted and calibrated in an adjustment window order to prevent injuries from loads that do approach the injury thresholds and to prevent inadvertent releases from skiing maneuvers, such as recoveries, that might produce loads that are larger than usual but still do not approach the potentially injurious, or harmful, loads.